Prediction of Automotive Interior Plastic Weathering Performance with Accelerated Weathering Techniques

Improving automotive interior part quality in order to enhance consumer satisfaction was studied by determining the long term retention of plastic aesthetics through vehicle exposure and current accelerated testing techniques. A joint project between General Motors and The Dow Chemical Company was initiated in 1986 to study and compare the performance of accelerated and real time exposure testing on interior plastic materials and to determine the ability of accelerated methods to predict vehicle performance. Prediction of interior vehicle weathering would shorten the product development cycle and prevent over or under-engineering of molded-in-color interior plastic materials. Under-engineering may lead to increased warranty costs and lower customer satisfaction, while over-engineering of plastic materials adds unnecessary cost to the vehicle.

The study included eleven polymers placed at thirty locations in vehicles in Arizona and Texas. Color measurements were taken over a five year period and correlated to data obtained by accelerated weathering, allowing predictive performance in a short time period. Results indicate the most stable polymers included in the study were the polyolefins (PP, PE) and styrenic resins (ABS, AES, and ASA) with ΔE values of less than 6 after five years in the 95th and 99th percentile severe solar environments. The greatest color change was measured in acetal and PVC with ΔE values as high as 40. The combined effect of temperature and ultraviolet (UV) exposure level on the eleven polymers included in the study was determined by comparing high, medium and low temperature locations with various UV exposure levels. The acceleration of color change due to increased temperature was found to be significant. The data obtained in this study will be used to set realistic specification requirements for various interior trim polymers and will allow informed material selection based on location of use in vehicles.